Enhancement of flavor and healthcare substances, mouthfeel parameters and collagen synthesis in the muscle of on-growing grass carp (Ctenopharyngodon idella) fed with graded levels of glutamine

Abstract The effects of dietary glutamine levels on growth performance, amino acid and fatty acid composition, mouthfeel parameters, collagen synthesis and related molecule expression in on-growing grass carp were assessed. Six iso‑nitrogenous diets differing in glutamine concentrations (0.02, 1.89, 4.07, 5.88, 7.86 and 11.92 g/kg) were fed to grass carp (169.7 ± 0.28 g) for 60 days. Results demonstrated that proper dietary glutamine levels (1) promoted the growth of grass carp; (2) increased muscle flavor amino acid, flavor nucleotide (IMP), flavor fatty acid (C18:2 and C18:3) and healthcare n-3 PUFA (EPA and DHA) contents; (3) improved the mouthfeel of fish muscle by increasing WHC, pH and shear force (firmness), which were partly related to increased Gln metabolites (Pro and Cit), decreased lactate content and LDH activity, and increased muscle fiber density and collagen content, respectively; (4) increased type I collagen synthesis partly associated with the activation of TGF-β1/Smads signalling in the muscle of fish. In conclusion, this study demonstrated for the first time that dietary glutamine could enhance muscle flavor and healthcare substances, mouthfeel parameters and type I collagen synthesis of fish.